First question: To be perfectly frank, there are very few (if any) personal statement topics that are truly "unique." I wouldn't worry too much about focusing on "uniqueness"--it can drive you crazy with overanalysis.
What
will make your personal statement stand out is how well it is written (the vast majority of statements are poorly written, which makes a carefully crafted/edited one stand out), and how you convey yourself within it. It's not about having a unique story, it's about making an impression in your reader's mind. You accomplish this by doing three things in your statement: talking about things you are passionate about, keeping the story focused on you, and telling anecdotes that exemplify the points you're trying to get across. If you feel that you can convey important attributes about yourself in a memorable, passionate way by talking about your athletic experiences, then go for it!
Second question: There's no magic number of schools to which you should apply. What you're suggesting is actually the perfect way to go about it--apply to a few "reach" schools (20% chance of acceptance or less), a few "definite" schools (75% chance of acceptance or more), and a good number of "target" schools (~50% chance of acceptance). You've got the right idea!
Third question: Schools do not expect you to write a specific personal statement for their school (and, if they do, they'll ask you in the form of an additional essay along the lines of "Why do you want to attend XYZ Law School?" or "Why XYZ Law School?"). Nonetheless, you can tailor the personal statement to each school if you want. It won't hurt. However, let me say this: Chances are pretty good you'll end up saying very similar things across the board (since it's likely you'll want each school to know about your good qualities, and you'll probably think of the same stories to convey them), and it can also be exhausting to write 5, 10, or 15 separate essays, worrying all while about making them sufficiently different from each other. If you've legitimately got something very specific to say to a school, don't hesitate in adding it to your already-existing essay, or by writing a brand-new essay to get your point across. But personalizing essays for the sake of personalizing essays isn't really, in my mind, the best way to spend your application time. Regarding mission statements and goals: Schools do not expect you to rattle these things back to them--instead, they expect to be presented with a cohesive image of you as a person. Don't focus so much on the school in your statement; focus on you, your qualities, your experiences, and your personality.
Fourth question: I have not heard of any definitive rumors doing away with the Wisconsin diploma privilege. There's always talk about it, given its unique nature. That's not to say that it couldn't be done away with while you're in school; the possibility always exists. Regarding going to school in the same state where you're considering practicing: That's always a good idea, specially if you attend a state school. Your network will be much stronger in-state, which could lead to better job opportunities. The legal market in general is struggling, so it might not give you much of an edge, but any edge you can get is a good one.
I hope that helps!
